Drug-resistant bacteria: Sewage-treatment plants described as giant 'mixing vessels' after scientists discover mutated microbes in British river

Steve Connor

Steve Connor is the Science Editor of The Independent and i. He has won many awards for his journalism, including five-times winner of the prestigious British science writers’ award; the David Perlman Award of the American Geophysical Union; four times highly commended as specialist journalist of the year in the UK Press Awards; UK health journalist of the year and a special merit award of the European School of Oncology for his investigations into the tobacco industry. He has a degree in zoology from the University of Oxford and has a special interest in genetics and medical science, human evolution and origins, climate change and the environment.

Superbugs resistant to some of the most powerful antibiotics in the medical arsenal have been found for the first time in a British river – with scientists pinpointing a local sewage-treatment plant as the most likely source.

Scientists discovered the drug-resistant bacteria in sediment samples taken downstream of the sewerage plant on the River Sowe near Coventry. The microbes contained mutated genes that confer resistance to the latest generation of antibiotics.

The researchers believe the discovery shows how antibiotic resistance has become widespread in the environment, with sewage-treatment plants now acting as giant “mixing vessels” where antibiotic resistance can spread between different microbes.

A study found that a wide range of microbes living in the river had acquired a genetic mutation that is known to provide resistance to third-generation cephalosporins, a class of antibiotics used widely to treat meningitis, blood infections and other hospital-acquired infections.

Within the river sediment, the scientists also found human gut bacteria that had developed resistance to another kind of antibiotic, called imipenem, which is administered by intravenous injections for severe infections not normally treatable with other antibiotics.

“These are frontline antibiotics and we were not expecting to see these kinds of levels of resistance to them in the environment. It is quite staggering,” said Professor Elizabeth Wellington of the University of Warwick, who led the study. “This is a worrying development and we need to be concerned about it. We’ve completely underestimated the role waste-treatment processes can play in antibiotic resistance,” she told The Independent.

Antimicrobial resistance occurs when bacteria evolve genetically so that they cannot be killed by antibiotic drugs
Tests have shown that the level of antibiotic resistance is many times higher downstream of the Coventry sewage-treatment facility than it is upstream. “The way sewerage plants mix up different types of waste means they’re hotspots, helping bacteria share genes that mean they can deactivate or disarm antibiotics that would normally kill them,” Professor Wellington said.

“This is a big deal, because this is the most common bacterial resistance gene causing failures in treatment of infections, and it’s the first time anyone has seen this gene in UK rivers,” she added.

“The problem is we use river water to irrigate crops, people swim or canoe in rivers, and both wildlife and food animals come into contact with river water. These bacteria also spread during flooding, and with more flooding and heavy rain this could get worse.”

Stricter regulations and higher levels of sewage treatment, with an emphasis on preventing untreated sewage being discharged during a storm, are needed to halt the rise of antibiotic resistance in the environment, Professor Wellington said.

“We’re on the brink of Armageddon and this is contributing to it. Antibiotics could just stop working,” she added.

Earlier this month, David Cameron warned that the world could be “cast back into the dark ages of medicine” where people die of relatively trivial and treatable infections caused by drug-resistant bacteria.

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